The present invention relates to textile machinery for producing twisted yarn and, more particularly, to single-process twisting machines for producing twisted yarn from two strands, e.g., cord yarn, threads for fishing nets and implements, etc.
There is known at present a single-process twisting machine for producing twisted yarn from two strands. This machine has work stations arranged along the longitudinal axis of the machine, with each work station including: a twisting spindle imparting the first twist and the second twist to the strands and incorporating an arbor with an axial passage and a radial passage, a twisting disc and a stationary holder of the bobbin of the supply package of the first strand associated with means for tensioning this strand, another holder of the bobbin of the supply package of the other strand arranged outside the twisting spindle and associated with means for tensioning this strand, a device for balancing the tensioning of the strands prior to imparting thereto the second twist forming the twisted yarn, a feed-in device, and a take-up mechanism and the respective drives of the twisting spindle, of the feed-in device, and of the take-up mechanism.
In this known machine the strand unwound from the bobbin of the stationary holder of the twisting spindle is fed directly into the tension balancing device, whereas the other strand unwound from the package of the holder arranged outside the spindle is fed into this device through the axial passage of the arbor and the twisting disc. This second strand, as it rotates, forms a balloon about the stationary holder.
An important requirement for normal operation of a single-process twisting machine is a timed starting and arresting of the mechanisms of any single work station, without the necessity of disabling the whole machine for the purpose.
This starting and arresting of any single work station, be it manual or automatic, is needed either to replace an exhausted supply package or to attend to breakage of either one of the two strands. The strands wound on the bobbins of the two supply packages being of different length, the bobbins are exhausted at different moments, and, consequently, when the supply package of either one of the strands is completely exhausted, it is necessary to arrest the work station, either manually or automatically, to prevent winding of a single-strand yarn on the take-up package.
However, the hitherto known single-process twisting machines are not provided with means for stopping any one of the work stations individually, without arresting the whole machine.
Another important requirement for profitable operation of the known single-process twisting machines is uniformity of the tensioning of the two strands prior to imparting the second twist thereto. Therefore, these machines incorporate a device mounted in the upper portion of the twisting spindle, on the stationary holder of the supply package, for balancing the tensioning of the strands.
The aforementioned arrangement of the balancing devices necessitates removal of these devices from the twisting spindles, as the packages are replaced, which increases downtime associated with package replacement and with threading the strands into this device. Furthermore, this arrangement is practically suitable solely for manual threading of the strands into the device for balancing their tension and precludes incorporation of automatic strand-threading means.
With the balancing devices arranged at the upper portion of the twisting spindle the conditions of tensioning of the two strands are not equal, which is reflected in a poorer quality of the yarn being produced, since the strand unwound from the package of the holder arranged outside the twisting spindle, as it forms a rotating balloon, imparts rotation to the device balancing the tensioning of the strands, and, consequently, is able to affect this balance of tensioning and the preset degree of tensioning.
With the device balancing the tensioning of the strands arranged at the upper portion of the twisting spindle and, therefore, inside the balloon, there evolves reduction of the maximum capacity of the package arranged on the stationary holder, since it is necessary to arrange below this device the means for tensioning the strand unwound from this package. Furthermore, the aforementioned feature impedes the provision of a device for balancing the tensioning of the strands, which would provide optimized conditions of paying the strand off packages of different shapes and ensure that the strand is uniformly tensioned throughout period of the gradual reduction of the volume of the package.